the theme....?

Question

sonnet 18

shall i compare thee to a summer's day?
thou art more lovely and more temperate?
rough winds do shake the darling buds of may,
and summer's lease hath all too short a date,
sometime too hot the eye of heaven shines,
and often is his gold complexion dimmed;
and every fair from fair declines,
by chance or nature's changing course untrimmed;
but thy eternal summer shall not fade;
nor loose possession of that fair ow'st,
nor shall death brag thou wond'rest in his shade,
when in eternal lines to time thou grow'st,
so long as men can breathe or eyes can see,
so long lives this, and this gives life to thee.

Answer 1

Love... everything, even the most beautiful things in nature pale in comparison to the object (recipient) of this poem

Answer 2

I think the theme is love and life. No matter what happens in life, the person he is talking about still remains lovely and true.